you shouldnt need an extra battery i run 2 top lights 55 watts each 2 side lights 55 watts each plus headlights and flashers and have had no power issure.LED lights take virtually no wattage to run so you should have no worries.
I just installed a 50" led lightbar on my 900. really really bright and pulls very little amperage.
I got mine at Plaslights league city. paid 395.00. Great light
Here is mine I have two 9 in ones on the front and 2 on the back which I bought off email 200 bucks for all and they are really great. Link to lights on eBay when you go there make sure you scroll down the page lots of other lights to choose from.